Mount Fuji Volcanic Stress

Here's Why You Might Want To Re-Think Your Upcoming Trip To Japan

For those of us who are neither geologists nor in Japan, it’s unlikely that we give much thought to Mount Fuji, the iconic Japanese peak. Well, lest we forget, science would like to not only remind us that it’s an active volcano, but thanks to 2011’s earthquake, it may well be more active than ever.

Mount Fuji sits atop a literal hotbed of activity, being located at the intersection of the Pacific, Eurasian and Philippine tectonic plates. For the past 300-plus years, it’s sat there quietly. Thanks to the 9.0 magnitude earthquake that caused a massive tsunami in March 2011, Mount Fuji is now under a great deal of pressure.

"Our work does not say that the volcano will start erupting, but it does show that it's in a critical state," Florent Brenguier, a researcher at the Institute of Earth Sciences (IST) in Grenoble, France, told the Guardian.

What happens is this: As you’re probably aware, an earthquake sends out shockwaves in concentric circles, and these shockwaves can travel vast distances. Because Mount Fuji sits atop a bunch of molten rock and gas, that foundation is even more susceptible to the the shockwaves than ordinary rock. When bombarded with such powerful forces, they exert a great deal of pressure, even though Mount Fuji is 250 miles from the quake’s epicenter. The fastest outlet for that pressure is up — usually through the mouth of an active volcano.

Brenguier and his team had to use some tricky methods to arrive at their conclusion. Thankfully, Japan’s Hi-net system is the densest seismic measurement system in the world, with some 800 sensors. That’s a lot of data. By focusing on otherwise imperceptible subterranean “noise,” they were able to create a virtual map of disturbances in Japan’s bedrock.

Does that mean Japan is doomed? Not necessarily, they say.

"We cannot establish a direct relation of cause and effect between quakes and volcanic eruptions, even if statistically the former lead to an increase in the latter," Brenguier says. "All we can say is that Mount Fuji is now in a state of pressure, which means it displays a high potential for eruption. The risk is clearly higher."